U.S. patent number 4,469,138 [Application Number 06/563,540] was granted by the patent office on 1984-09-04 for pipes made of polypropylene reinforced with carbon fibers.
This patent grant is currently assigned to Kureha Kagaku Kogyo Kabushiki Kaisha. Invention is credited to Hiroaki Satoh.
United States Patent |
4,469,138 |
Satoh |
September 4, 1984 |
Pipes made of polypropylene reinforced with carbon fibers
Abstract
Pipes of polypropylene reinforced with carbon fibers comprising
100 parts by weight of polypropylene, 10 to 40 parts by weight of a
modified polypropylene by an organic unsaturated carboxylic acid or
a copolymer of propylene and the organic unsaturated carboxylic
acid and 5 to 70 parts by weight of carbon fibers of 5 to 30
micrometers in diameter and a ratio of diameter to length of 10 or
more. The rate of retention of the original tensile strength of
pipe in boiling water for 6 months at 100.degree. C. was higher
than 95%.
Inventors: |
Satoh; Hiroaki (Tokyo,
JP) |
Assignee: |
Kureha Kagaku Kogyo Kabushiki
Kaisha (Tokyo, JP)
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Family
ID: |
13245437 |
Appl.
No.: |
06/563,540 |
Filed: |
December 20, 1983 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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288798 |
Jul 31, 1981 |
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Foreign Application Priority Data
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May 16, 1980 [JP] |
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55/63998 |
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Current U.S.
Class: |
138/174;
428/36.4; 524/496; 138/177; 524/495; 524/522 |
Current CPC
Class: |
C08L
23/12 (20130101); C08L 23/26 (20130101); C08L
23/14 (20130101); F24D 3/146 (20130101); F16L
9/128 (20130101); C08K 7/06 (20130101); C08K
7/06 (20130101); C08L 23/12 (20130101); C08L
23/12 (20130101); C08L 2666/24 (20130101); C08L
23/12 (20130101); C08L 23/26 (20130101); C08K
7/06 (20130101); C08L 23/12 (20130101); C08L
23/14 (20130101); C08K 7/06 (20130101); Y02P
20/124 (20151101); B29K 2023/12 (20130101); B29K
2307/00 (20130101); Y10T 428/1372 (20150115); Y02B
30/00 (20130101); B29C 48/09 (20190201); Y02B
30/24 (20130101); B29C 48/15 (20190201); B29L
2023/22 (20130101); B29K 2105/12 (20130101) |
Current International
Class: |
B29C
47/00 (20060101); F24D 3/14 (20060101); F24D
3/12 (20060101); F16L 9/00 (20060101); F16L
9/128 (20060101); C08L 23/00 (20060101); C08L
23/12 (20060101); C08K 7/06 (20060101); C08K
7/00 (20060101); F16L 009/00 () |
Field of
Search: |
;138/174,177 ;428/36
;524/495,496,522 |
References Cited
[Referenced By]
U.S. Patent Documents
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4057610 |
November 1977 |
Goettler et al. |
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Foreign Patent Documents
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2324382 |
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Feb 1974 |
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DE |
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1251641 |
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Oct 1971 |
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GB |
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1442527 |
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Jul 1976 |
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GB |
|
Primary Examiner: Dixon, Jr.; William R.
Attorney, Agent or Firm: Finnegan, Henderson, Farabow,
Garrett & Dunner
Parent Case Text
This application is a continuation, of application Ser. No.
06/288,798, filed July 31, 1981, now abandoned.
Claims
What is claimed is:
1. A pipe for hot water of polypropylene reinforced with carbon
fibers made from a composite material consisting essentially
of:
(a) 100 parts by weight of polypropylene;
(b) 10 to 40 parts by weight of a modified polypropylene selected
from the group of: (1) polypropylene modified by the chemical
addition of from 1 to 8 parts by weight of an organic unsaturated
carboxylic acid per 100 parts by weight of polypropylene, said acid
being selected from the group consisting of maleic acid, acrylic
acid, methacrylic acid, fumaric acid, endobicyclo (2.2.1)2,
3-dicarboxylic acid and their anydrides; and (2) propylene
copolymerized with from 1 to 8 parts by weight of said carboxylic
acid per 100 parts by weight of said propylene; and
(c) from 5 to 70 parts by weight of carbon fibers having a diameter
of from 5 to 30 micrometers and a ratio of diameter to length of at
least 10.
2. The pipe of claim 1, wherein the modified polypropylene is
polypropylene modified by the chemical addition of maleic acid.
3. The pipe of claim 1, wherein the modified polypropylene is a
copolymer of propylene and acrylic acid.
Description
SUMMARY OF THE INVENTION
The present invention provides novel pipes made of reinforced
polypropylene which exhibit excellent strength even in boiling
water. The main characteristic feature of the present invention is
that the pipe is prepared by shaping a resin composition comprising
polypropylene as the base material, modified polypropylene prepared
by partially modifying polypropylene with an organic unsaturated
carboxylic acid or by copolymerizing propylene and the organic
unsaturated carboxylic acid and short carbon fibers. A
characteristic feature of the thus prepared pipe is that the ratio
of mechanical strength after holding the pipe for 6 months in
boiling water at 100.degree. C., to the original strength if higher
than 95%.
BRIEF EXPLANATION OF DRAWING
FIG. 1 shows the relationship between the tensile strength and the
amount of modified polypropylene in the pipe of this invention;
FIG. 2 shows the relationship between the rate of retention of the
original tensile strength of the pipe with time in boiling
water;
FIG. 3 shows the relationship between the tensile strength of the
pipe and the content of carbon fiber at various temperatures;
FIG. 4 shows the relationship between the melt index of the polymer
composition and the carbon fiber content; and
FIG. 5 shows the relationship between the linear thermal expansion
coefficient of the pipe and the carbon fiber content.
FIG. 1, which shows the relationship between the tensile strength
and the amount of modified polypropylene in a pipe, the composition
contained polypropylene, modified polypropylene and carbon fiber
(45 parts by weight per 100 parts of polypropylene). Curve 1 shows
that of pipe containing modified polypropylene with maleic acid and
Curve 2 shows that of pipe containing a copolymer of propylene and
acrylic acid. In FIG. 2, which shows the rate of retention of the
original tensile strength of a pipe, the composition was 45 parts
by weight of carbon fiber, 30 parts by weight of modified
polypropylene and 100 parts of polypropylene and the pipe was kept
in boiling water at 100.degree. C. Curve 1 shows the relationship
in the pipe in which the modified polypropylene was obtained by
chemically treating polypropylene with maleic acid to contain 2
parts by weight of maleic acid units per 100 parts by weight of
propylene units. Curve 2 shows the relationship in the pipe in
which the modified polypropylene was obtained by copolymerizing
propylene and acrylic acid to contain 6 parts by weight of acrylic
acid units per 100 parts by weight of propylene units. Curve 3
shows the relationship in a conventional reinforced polypropylene
pipe containing 45 parts by weight of glass fiber per 100 parts by
weight of polypropylene. In FIGS. 3 to 5, the compositin of the
pipes and the composite material, except for carbon fibers, was 100
parts by weight of polypropylene and 30 parts by weight of modified
polypropylene.
BACKGROUND OF THE INVENTION
Shaped articles and pipes able to withstand hot water at
100.degree. C. have been used not only for industrial purposes but
also, particularly, in recent years in pipings of central heating
in homes in a large amount. As a synthetic resin for preparing such
pipes to withstand hot water (boiling water at 100.degree. C.),
fluoropolymers, thermosetting resin reinforced by fibers or
chlorinated polyvinyl chloride have been utilized. However,
fluoropolymers cannot be generally used because of their poor
processability and high price. Thermosetting resin reinforced by
fibers is not suitable for mass production owing to its
thermosetting property and chlorinated polyvinyl chloride is also
not suitable for the purpose because its thermal resistence is at
most 100.degree. C. and because of its poor processability.
On the other hand, although polypropylene, a thermoplastic resin,
is favorably processable and thermally resistant for use in such a
temperature range, its coefficient of thermal expansion in a
temperature range of 50.degree. to 100.degree. C. is as large as
18.times.10.sup.-5 /.degree. C. Accordingly, the deformation and
displacement of a long pipe made of polypropylene is fairly large
and in the case where the deformation and displacement is
mechanically restrained, an accumulation of internal stress cause
the pipe to break.
In order to make up for such a deficiency, an addition of a filler
into the base material has been proposed. Taking into account the
improvement of its strength, glass fibers have been used as the
filler. However, it was found by the present inventor that
polypropylene reinforced by glass fibers showed a conspicuous
reduction of strength in boiling water. For instance, polypropylene
reinforced by 45% by weight of glass fibers showed a conspicuous
deterioration in strength with time as is seen in Curve 3 in FIG.
2. The use of carbon fibers instead of glass fibers has been
proposed, but the reduction of its strength during a long term
immersion in boiling water at 100.degree. C. could not be
prevented.
Accordingly, a solution to the problem of the reduction of
mechanical strength during the immersion for a long period in
boiling water has been sought in various fields.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is based on the finding that pipe
manufactured by shaping a composite material comprising 100 parts
by weight of polypropylene, 10 to 40 parts by weight of modified
polypropylene prepared by modifying a part of polypropylene with an
organic unsaturated carboxylic acid of 3 to 10 carbon atoms or by
copolymerizing the organic unsaturated carboxylic acid and
propylene and 5 to 70 parts by weight of carbon fibers shows a
small thermal expansion coefficient in boiling water at 100.degree.
C. and retains its original strength for a long time period in
boiling water at 100.degree. C.
Modified polypropylene a which is one of the most important factors
in the present invention, means a chemically treated polypropylene
obtained by modifying a part of a molecule of polypropylene with an
organic unsaturated carboxylic acid of 3 to 10 carbon atoms or a
copolymer of the organic unsaturated carboxylic acid and propylene.
The degree of modification of polypropylene is in a range of 0.5 to
8%, preferably, 1 to 6%. An organic unsaturated carboxylic acid for
use in the present invention is maleic acid, acrylic acid,
methacrylic acid, fumaric acid, endobicyclo[2.2.1]2,3-dicarboxylic
acid and the likes and their anhydrides. Maleic acid and acrylic
acid are preferable.
In the case where the amount of the modified polypropylene is
smaller than that mentioned above, the reduction in strength
becomes larger as shown in FIG. 1 resulting it being insufficient
for use in the intended purpose. On the other hand, in the case
where the amount is larger than that mentioned above, a tendency in
the reduction of thermal resistance is seen. Also the use of a
larger amount of the modified polypropylene is not preferable from
the view point of its cost.
In the present invention, the carbon fibers for use in reinforcing
are 5 to 30 micrometers in diameter and higher than 10 in the
aspect ratio (ratio of length to diameter). In addition, in order
to enhance the adhesiveness of carbon fibers to polypropylene, the
carbon fibers may be treated by surface-coating. For example,
aminopropyltrioxysilane or vinylethoxysilane can be used to coat
the surface of the carbon fibers.
Generally, the tensile strength of the material comprising
polypropylene reinforced with carbon fibers is improved with an
increase of the amount of carbon fibers in the material, the
tendency being the saame at any one temperature from ordinary
temperature to nearly 100.degree. C. as is seen in FIG. 3. While
the tensile strength is generally smaller at higher temperatures,
the reduction in strength due to the temperature raise is largely
prevented by the addition of carbon fibers into the composite
material for shaping the pipe. Thus it is preferable to add carbon
fibers in a large amount into polypropylene for the general
improvement of the tensile strength of the shaped material.
However, the melt fluidity of the composite material can be
influenced by too much carbon fibers to the point where the
processability of the composite material at molding becomes low.
This situation will be understood from FIG. 4 wherein the melt
index of the composition is referred to ASTM D-1238. In the case
where the pipe according to the present invention is to be prepared
by extrusion shaping the composite material, it can contain carbon
fibers up to 70 parts by weight per 100 parts by weight of
polypropylene and still processable. However, the preferable amount
is around 50 parts by weight per 100 parts by weight of
polypropylene from the view point of processability.
In addition, the linear thermal expansion coefficient of the pipe
made of composite material comprising polypropylene and carbon
fibers is reduced with a content of carbon fibers higher than about
5 parts by weight per 100 parts by weight of polypropylene as is
seen in FIG. 5. For example, the linear thermal expansion
coefficients of pipes containing carbon fibers in the amounts of 0,
5 and 10 parts by weight per 100 parts by weight of polypropylene
are 18-, 13- and 10.5 .times.10.sup.-5 /.degree. C., respectively.
This large difference between the coefficients indicates the effect
of carbon fibers on the dimensional stability of the pipe.
In conclusion, considering all of the above while taking into
account the meaning of the illustrations in FIGS. 3 to 5, a
suitable amount of carbon fibers in the pipe is from about 5 to 70
parts by weight per 100 parts by weight of polypropylene.
Pipe manufacture according to the present invention by shaping a
composite material comprising reinforced polypropylene containing 5
to 70 parts by weight of carbon fibers per 100 parts by weight of
polypropylene, differs from pipe shaped from polypropylene
reinforced with glass fibers, because it has a small linear thermal
expansion coefficient and shows only a slight deterioration while
retaining more than 95% of the original strength even after a long
period of use in boiling water at 100.degree. C. Accordingly, the
pipe of the present invention can be advantageously utilized in
industrial and home uses for hot water.
The present invention will be further explained in detail while
referring to non-limiting examples as follows:
EXAMPLE 1
Starting from a composite material comprising 100 parts by weight
of polypropylene (product of Tonen Petrochemical Co., Ltd., Grade
J-209 of melt index of 9.0), 30 parts by weight of modified
polypropylene of melt index of 20.0 and melting point of
162.degree. C., prepared by the chemical addition of 2 parts by
weight of maleic acid to 100 parts by weight of polypropylene, and
45 parts by weight of carbon fiber of 14.5 micrometers in diameter
and an aspect ratio of 50 (prepared by Kureha Kagaku Kogyo
Kabushiki Kaisha, Grade M 107), pipes of reinforced polypropylene
with carbon fibers having a wall thickness of 3 mm and 1 inch in
nominal diameter were manufactured by extrusion shaping. While
continuously immersing the thus manufactured pipe in boiling water
at 100.degree. C., test pieces were collected every moth during 6
months to be tested on their change of tensile strength, the
results being shown in FIG. 2. As is seen in Curve 1 in FIG. 2, the
rate of retention of the original tensile strength did not show any
change during 6 months and showed a significant and excellent
difference as compared to that of the pipe of reinforced
polypropylene with glass fiber as shown by Curve 3. Thus the pipe
according to the present invention would be good for practical
uses.
EXAMPLE 2
Pipes were prepared under the same conditions as in Example 1
except a copolymer of melt index of 50 and melting point of
168.degree. C., obtained by copolymerizing a mixture of 94 parts by
weight of propylene and 6 part by weight of acrylic acid was used
instead of the modified polypropylene with maleic acid in Example
1. As is seen in Curve 2 of FIG. 1, pipes prepared from this
material had excellent characteristics.
* * * * *